def fac(k) :
    i = 2
    t = 1
    while i <= k:
     t *= i
     i += 1
    return  t
def sum(n) :
    s = 0
    i = 1
    while i <= n:
        s = s + fac(i)
        i += 2
    return s
print('1!+4!+7!...50!=', sum(50))

